1. Field of the Invention
The present invention relates to a system for exhausting the combustion gases of an internal combustion engine, comprising an exhaust manifold, means for exhausting said gases, connected to said manifold and likely to clog, and a pressure sensor communicating with said manifold.
2. Description of the Prior Art
Such a system is already known described in the patent application No. GB-A-2 134 408. In this system, the internal combustion engine is a diesel engine for a motor vehicle, and the means for exhausting the combustion gases comprise a filter, made from ceramics or a metal grid, for retaining the particles contained in said gases. After a certain time, the amount of particulates retained in such that the filter finishes by clogging. This results in a rise of the pressure of the gases in the exhaust manifold, as well as in the cylinders of the engine, called "back pressure". When this back pressure exceeds a certain threshold, specified by the constructor of the engine, the combustion is poor and causes a loss of power.
It is then necessary to regenerate the filter, that is to say, here, to free it of the particulates which clog it, by subjecting it to a flow of very hot gas, at a temperature greater than 550.degree. C. With the pressure sensor, it is possible to proceed with the regeneration of the filter as soon as the back pressure in the exhaust manifold exceeds a given threshold, i.e. at the optimum time, having regard to the clogging of the filter.
A similar problem arises for the flame proof exhaust systems for internal combustion engines used in particular on oil drilling platforms. Thus, there exists such a system in which the means for removing the exhaust gases are flame proof and comprise for example a stack of washers which may become clogged. Such a stack, described in French Pat. No. FR-1 498 492 is formed of bored washers of appropriate thickness and spacing. Its function is in particular to laminate the exhaust gases and extinguish the incandescent carbon particles which they contain. It finishes therefore by being clogged up after a varying time. In this system, which does not comprise any pressure sensor communicating with the exhaust manifold, the flame proof stack is changed systematically after a time sufficiently short for it to be certain that the stack has not yet become too clogged, which has the following disadvantages: on the one hand, it may thus be necessary to replace the stacks too often, which results in a loss of time and, on the other hand, the replacement of the stack takes a certain time, during which the engine is shut down, which is costly, in particular an oil drilling platforms where these flame proof systems are used. Finally, experience shows that the operator tends to be negligent and not to replace and maintain the stack as required.
To overcome these disadvantages the teaching of the patent application No. GB-A-2 134 408 may of course be used for attempting to measure the back pressure of the combustion gases inside the exhaust manifold by means of a pressure sensor.
Unfortunately, because of the very high and fluctuating temperature of the combustion gases in engines for oil platforms and of the incandescent particles which they contain, it is not possible to use a conventional type membrane pressure sensor, as the one used in the patent application No. GB-A-2 134 408. A special sensor must therefore be used, of a high cost price, provided that it is feasible.
In addition, the output of such a sensor is generally electric. Now, the rules and recommendations concerning flameproof enclosures are very strict concerning the electric voltages and currents in their vicinity, which introduces an additional constraint.
A practical solution consists in forming an opening in the exhaust manifold, opening into a duct placing it in communication with a pressure sensor, situated in a less disturbed environment.
In this case, however, the rules and recommendations concerning flame proof enclosures are no longer respected.
The present invention overcomes the preceding problems.